In the art of satellite communications, the modern antennas on board of satellites are frequently implemented by an active/passive array of feeds in the focal plane of a reflector system when using orthogonally polarized signals in the feed systems. The cluster of feeds is arranged closely side by side causing implementation problems due to their often complex shape, especially when a great number of feeds are used in a compact configuration. Therefore, the feed waveguide configurations become very intricate and it is important to reduce the size of the feeds in the X and Y axes (with Z being the propagation axis). If the radiating element of the feed is small, the limiting factor that prevents the size reduction is the orthomode transducer (OMT).
The OMT is a waveguide-component capable of dividing an orthogonally polarized electro-magnetic signal into two linearly polarized signals and, in reverse direction, capable of combining two linearly polarized signals into an orthogonally polarized electro-magnetic signal. It is therefore desirable for OMTs used in feed systems comprising a plurality of closely located signal sources to be compact and to have minimum complexity.
Several types of OMT devices are known in the art. Complex OMTs such as coaxial OMTs, Boifot OMTs, ortho-mode junctions or turnstile junctions offer good bandwidth and/or power handling. However, feed systems using the above types of OMT devices face assembling problems, e.g., due to the need for complicated waveguide networks to recombine all the ports, especially when a great number of signal sources have to be fed and when the sources are close to each other.
A further type of an OMT, a side-coupling OMT, is disclosed in FR 2904478 A1 and by Chattopadhyay et al. in Microwave and Guided Wave Letters, IEEE, Vol 8, Issue 12, December 1998, pages 421-423. This type of OMT apparatus is more compact than the complex OMTs but requires a coupling area with a slot iris of small dimensions that reduces drastically the power handling of the device.
In view of the above problems of the prior art, it is an object of the invention to provide an OMT device that is compact, has a low mass and is cost-efficient to manufacture. It is a further object of the invention to provide an OMT with high power handling capabilities.